4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <[email protected]> commit 60d3450167433f2d099ce2869dc52dd9e7dc9b29 upstream. Calling get_cpu_cap() will reset a bunch of CPU features. This will cause the system to lose track of force-set and force-cleared features in the words that are reset until the end of CPU initialization. This can cause X86_FEATURE_FPU, for example, to change back and forth during boot and potentially confuse CPU setup. To minimize the chance of confusion, re-apply forced caps every time get_cpu_cap() is called. Signed-off-by: Andy Lutomirski <[email protected]> Reviewed-by: Borislav Petkov <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Matthew Whitehead <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: One Thousand Gnomes <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Yu-cheng Yu <[email protected]> Link: http://lkml.kernel.org/r/c817eb373d2c67c2c81413a70fc9b845fa34a37e.1484705016.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/kernel/cpu/common.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -848,6 +848,13 @@ void get_cpu_cap(struct cpuinfo_x86 *c) init_scattered_cpuid_features(c); init_speculation_control(c); + + /* + * Clear/Set all flags overridden by options, after probe. + * This needs to happen each time we re-probe, which may happen + * several times during CPU initialization. + */ + apply_forced_caps(c); } static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
